need help

[Bande1]

quick backstory: I was gifted a bare hull, my first ever rc boat, and I built it out. it was an aquacraft supervee 27. so I took it on its maiden voyage today. it did quite well. BUT I was never able to open the throttle completely. even with quite calm water the boat would get unstable over about 55mph. 57mph was my top speed at about 75-80% throttle. I think that its lifting too much. I tried negative, positive, and neutral strut angles. I only have 1 metal prop (TFL 50mm) and a few plastic props to try.

what is a super low lifting prop? nobody really seems to list their rake angle. so far I have found the ABC 4555 not a single clue what the rake is.

[larryrose11]

Lifting the bow, or lifting the stern?
IN the RC boating world, people usually say a lifting prop is lifting the stern.
Sounds like you may need a prop the provides more lift to the stern, forcing the front down.

The higher rake angle tightens the thrust cone, and makes a prop with less lift.
Most of the ABC props list their rake angle.
For example a 2014-10-50(2) CLL breaks down like this.
20 is the diameter in inches.
1.4 Pitch Radio
10-RAKE ANGLE
50-BLADE AREA RATIO
(2)-NUMBER OF BLADES
CL-CLEAVER OR CP-CHOPPER
L-LEFT ROTATION OR R-RIGHT ROTATION

A props Rake angle is measurable if the prop shaft horizontal.

I'm sure that someone on the forum has experience with this hull.

[Bande1]

the entire hull is out of the water. the bow is flat, trim tabs are far out of the water even. literally riding on the keel at 55+ mph. Searching this forum people mentioned this hull simply isnt made to go faster than 50mph. It seem they're correct. I went out for further testing today with maybe modest improvement at best with +2 degree stinger angle. I was able to hold full throttle for about 1-2 seconds. 61mph. shes done and the motor wasnt even 85f. I will pull this motor an ESC and put something smaller in the boat. thinking about building an outrigger or something for this ones motor/esc.

[fweasel]

You can move battery weight forward in the hull if its airing out too much, and you're not able to get much change out of altering the trim angle. Lowering trim tabs will also for the bow down, at the expense of speed. I agree, you've running that hull faster than it was designed, and while fun, it's not necessarily a beast you can tame.

[Fluid]

Yes, the SuperVee 27 was simply not designed for speeds in excess of 40-45 mph, it has too much lift for stability above that speed. There are a few tricks to help keep it on the water at higher speeds - but there are still limits.

- add 6-8 ounces of lead at the CG
- raise the stinger drive about 1/4? to 3/8? above its current location (depending on prop diameter)
- use props with low lifting characteristics

The above have raised the lifting threshold in the past, but expecting a stable boat at 65-70 mph isn?t going to happen. Good idea to put in a less powerful motor and slip this high powered setup in a hull designed to go fast.


.

[Bande1]

Yes, the SuperVee 27 was simply not designed for speeds in excess of 40-45 mph, it has too much lift for stability above that speed. There are a few tricks to help keep it on the water at higher speeds - but there are still limits.

- add 6-8 ounces of lead at the CG
- raise the stinger drive about 1/4? to 3/8? above its current location (depending on prop diameter)
- use props with low lifting characteristics

The above have raised the lifting threshold in the past, but expecting a stable boat at 65-70 mph isn?t going to happen. Good idea to put in a less powerful motor and slip this high powered setup in a hull designed to go fast.


.

are you saying re-drill the transom and move the stuffing tube higher?

[Panchothedog]

YES. But it makes a lot more sense to just run the boat in the 40 mph range. The speed the hull was intended to run at. Lots of fun can be had at that speed, AND Lots of other hulls are available that can run at the 70mph
range and live to run again another day. Just not that one.

[Bande1]

YES. But it makes a lot more sense to just run the boat in the 40 mph range. The speed the hull was intended to run at. Lots of fun can be had at that speed, AND Lots of other hulls are available that can run at the 70mph
range and live to run again another day. Just not that one.

I turned her down to 75% today and held her wide open around the course. was fun. I ordered larger adjustable trim tabs. $10 cant hurt to try them.

[Bande1]

Ok I have fixed the problem. this boat now runs smoother than a babies bottom. It was the stock trim tabs. Got new, larger, adjustable trim tabs and moved them toward the keel 18mm. Night and day difference.